Herpes viruses are large double stranded DNA viruses that are responsible for a number of human diseases including chicken pox, shingles, fever blisters, salivary gland virus disease, and infectious mononucleosis. The seven human herpes viruses that have been described thus far are HSV-1, HSV-2, cytomegalovirus (CMV), Epstein-Barr Virus (EBV), varicella zoster virus (VZV), HHV-6, and HHV-7.
Maturation of herpes virus particles is believed to occur through the formation of a procapsid structure, which acquires DNA and an envelope to become an infectious virion. A herpes virus group-common protein referred to as the assembly protein in CMV, and as p40, VP22a, NCP-3, and ICP35e in HSV-1, is an abundant constituent of the herpes virus procapsid. The assembly protein is phosphorylated and proteolytically processed from a precursor molecule. It is absent from the mature virion, although its fate is unknown. These characteristics of the assembly protein have suggested an analogy between it and the bacteriophage scaffolding protein, which is an essential component for phage assembly but is not found in mature virus particles (Gibson et al. (1991) J. Virol. 64:1241-1249).
The proteolytic processing of the assembly protein has been implicated as a critical step in the maturation of the virus. A temperature sensitive (ts) mutant that is unable to process the HSV assembly protein homolog (p40) is incapable of producing DNA-containing capsids or virions (Preston et al. (1983) J. Virol. 45:1056-1064). Maturational processing of the simian CMV (SCMV) Colburn assembly protein results in loss of its carboxy terminus. (Gibson, 1991, supra.)
Up until the present time the enzyme responsible for the proteolytic maturation of the assembly protein has not been identified. Further, there is a need in the art for new agents for therapeutic treatment of herpes viruses.